1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_SCHED_TASK_H
3 #define _LINUX_SCHED_TASK_H
4
5 /*
6 * Interface between the scheduler and various task lifetime (fork()/exit())
7 * functionality:
8 */
9
10 #include <linux/sched.h>
11 #include <linux/uaccess.h>
12
13 struct task_struct;
14 struct rusage;
15 union thread_union;
16 struct css_set;
17
18 /* All the bits taken by the old clone syscall. */
19 #define CLONE_LEGACY_FLAGS 0xffffffffULL
20
21 struct kernel_clone_args {
22 u64 flags;
23 int __user *pidfd;
24 int __user *child_tid;
25 int __user *parent_tid;
26 const char *name;
27 int exit_signal;
28 u32 kthread:1;
29 u32 io_thread:1;
30 u32 user_worker:1;
31 u32 no_files:1;
32 unsigned long stack;
33 unsigned long stack_size;
34 unsigned long tls;
35 pid_t *set_tid;
36 /* Number of elements in *set_tid */
37 size_t set_tid_size;
38 int cgroup;
39 int idle;
40 int (*fn)(void *);
41 void *fn_arg;
42 struct cgroup *cgrp;
43 struct css_set *cset;
44 };
45
46 /*
47 * This serializes "schedule()" and also protects
48 * the run-queue from deletions/modifications (but
49 * _adding_ to the beginning of the run-queue has
50 * a separate lock).
51 */
52 extern rwlock_t tasklist_lock;
53 extern spinlock_t mmlist_lock;
54
55 extern union thread_union init_thread_union;
56 extern struct task_struct init_task;
57
58 extern int lockdep_tasklist_lock_is_held(void);
59
60 extern asmlinkage void schedule_tail(struct task_struct *prev);
61 extern void init_idle(struct task_struct *idle, int cpu);
62
63 extern int sched_fork(unsigned long clone_flags, struct task_struct *p);
64 extern void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs);
65 extern void sched_post_fork(struct task_struct *p);
66 extern void sched_dead(struct task_struct *p);
67
68 void __noreturn do_task_dead(void);
69 void __noreturn make_task_dead(int signr);
70
71 extern void mm_cache_init(void);
72 extern void proc_caches_init(void);
73
74 extern void fork_init(void);
75
76 extern void release_task(struct task_struct * p);
77
78 extern int copy_thread(struct task_struct *, const struct kernel_clone_args *);
79
80 extern void flush_thread(void);
81
82 #ifdef CONFIG_HAVE_EXIT_THREAD
83 extern void exit_thread(struct task_struct *tsk);
84 #else
exit_thread(struct task_struct * tsk)85 static inline void exit_thread(struct task_struct *tsk)
86 {
87 }
88 #endif
89 extern __noreturn void do_group_exit(int);
90
91 extern void exit_files(struct task_struct *);
92 extern void exit_itimers(struct task_struct *);
93
94 extern pid_t kernel_clone(struct kernel_clone_args *kargs);
95 struct task_struct *copy_process(struct pid *pid, int trace, int node,
96 struct kernel_clone_args *args);
97 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
98 struct task_struct *fork_idle(int);
99 extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
100 unsigned long flags);
101 extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
102 extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
103 int kernel_wait(pid_t pid, int *stat);
104
105 extern void free_task(struct task_struct *tsk);
106
107 /* sched_exec is called by processes performing an exec */
108 #ifdef CONFIG_SMP
109 extern void sched_exec(void);
110 #else
111 #define sched_exec() {}
112 #endif
113
get_task_struct(struct task_struct * t)114 static inline struct task_struct *get_task_struct(struct task_struct *t)
115 {
116 refcount_inc(&t->usage);
117 return t;
118 }
119
120 extern void __put_task_struct(struct task_struct *t);
121 extern void __put_task_struct_rcu_cb(struct rcu_head *rhp);
122
put_task_struct(struct task_struct * t)123 static inline void put_task_struct(struct task_struct *t)
124 {
125 if (!refcount_dec_and_test(&t->usage))
126 return;
127
128 /*
129 * In !RT, it is always safe to call __put_task_struct().
130 * Under RT, we can only call it in preemptible context.
131 */
132 if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
133 static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP);
134
135 lock_map_acquire_try(&put_task_map);
136 __put_task_struct(t);
137 lock_map_release(&put_task_map);
138 return;
139 }
140
141 /*
142 * under PREEMPT_RT, we can't call put_task_struct
143 * in atomic context because it will indirectly
144 * acquire sleeping locks.
145 *
146 * call_rcu() will schedule delayed_put_task_struct_rcu()
147 * to be called in process context.
148 *
149 * __put_task_struct() is called when
150 * refcount_dec_and_test(&t->usage) succeeds.
151 *
152 * This means that it can't "conflict" with
153 * put_task_struct_rcu_user() which abuses ->rcu the same
154 * way; rcu_users has a reference so task->usage can't be
155 * zero after rcu_users 1 -> 0 transition.
156 *
157 * delayed_free_task() also uses ->rcu, but it is only called
158 * when it fails to fork a process. Therefore, there is no
159 * way it can conflict with put_task_struct().
160 */
161 call_rcu(&t->rcu, __put_task_struct_rcu_cb);
162 }
163
DEFINE_FREE(put_task,struct task_struct *,if (_T)put_task_struct (_T))164 DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T))
165
166 static inline void put_task_struct_many(struct task_struct *t, int nr)
167 {
168 if (refcount_sub_and_test(nr, &t->usage))
169 __put_task_struct(t);
170 }
171
172 void put_task_struct_rcu_user(struct task_struct *task);
173
174 /* Free all architecture-specific resources held by a thread. */
175 void release_thread(struct task_struct *dead_task);
176
177 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
178 extern int arch_task_struct_size __read_mostly;
179 #else
180 # define arch_task_struct_size (sizeof(struct task_struct))
181 #endif
182
183 #ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST
184 /*
185 * If an architecture has not declared a thread_struct whitelist we
186 * must assume something there may need to be copied to userspace.
187 */
arch_thread_struct_whitelist(unsigned long * offset,unsigned long * size)188 static inline void arch_thread_struct_whitelist(unsigned long *offset,
189 unsigned long *size)
190 {
191 *offset = 0;
192 /* Handle dynamically sized thread_struct. */
193 *size = arch_task_struct_size - offsetof(struct task_struct, thread);
194 }
195 #endif
196
197 #ifdef CONFIG_VMAP_STACK
task_stack_vm_area(const struct task_struct * t)198 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
199 {
200 return t->stack_vm_area;
201 }
202 #else
task_stack_vm_area(const struct task_struct * t)203 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
204 {
205 return NULL;
206 }
207 #endif
208
209 /*
210 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
211 * subscriptions and synchronises with wait4(). Also used in procfs. Also
212 * pins the final release of task.io_context. Also protects ->cpuset and
213 * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist.
214 *
215 * Nests both inside and outside of read_lock(&tasklist_lock).
216 * It must not be nested with write_lock_irq(&tasklist_lock),
217 * neither inside nor outside.
218 */
task_lock(struct task_struct * p)219 static inline void task_lock(struct task_struct *p)
220 {
221 spin_lock(&p->alloc_lock);
222 }
223
task_unlock(struct task_struct * p)224 static inline void task_unlock(struct task_struct *p)
225 {
226 spin_unlock(&p->alloc_lock);
227 }
228
229 #endif /* _LINUX_SCHED_TASK_H */
230